Экранирующие свойства композитных материалов на основе эпоксидных смол с графеновыми нанопластинками в СВЧ-диапазоне частот

Проведен анализ электромагнитных свойств композитных материалов на основе эпоксидной смолы с добавлением 0.5 wt% графеновых нанопластинок в диапазоне частот 26-37 GHz. Определено влияние типа эпоксидной смолы, отличающейся вязкостью, и типа используемого растворителя (этанол, ацетон) на электромагнитный отклик в рассматриваемом диапазоне частот. Установлено, что наиболее эффективными для создания экранирующих покрытий в СВЧ-диапазоне являются наименее вязкая эпоксидная смола Epikote 828 и растворитель этанол. Композитные материалы оптимального состава обеспечивают ослабление электромагнитного сигнала по мощности на уровне не менее 10 dB при толщине пленки 1.1 mm

Designing cascades of electron transfer processes in multicomponent graphene conjugates

A novel family of nanocarbon-based materials was designed, synthesized, and probed within the context of charge-transfer cascades. We integrated electron-donating ferrocenes with light-harvesting/electron-donating (metallo)porphyrins and electron-accepting graphene nanoplates (GNP) into multicomponent conjugates. To control the rate of charge flow between the individual building blocks, we bridged them via oligo-p-phenyleneethynylenes of variable lengths by β-linkages and the Prato-Maggini reaction. With steady-state absorption, fluorescence, Raman, and XPS measurements we realized the basic physico-chemical characterization of the photo- and redox-active components and the multicomponent conjugates. Going beyond this, we performed transient absorption measurements and corroborated by single wavelength and target analyses that the selective (metallo)porphyrin photoexcitation triggers a cascade of charge transfer events, that is, charge separation, charge shift, and charge recombination, to enable the directed charge flow. The net result is a few nanosecond-lived charge-separated state featuring a GNP-delocalized electron and a one-electron oxidized ferrocenium

Improved understanding of self-sustained, sub-micrometric multi-composition surface Constantan wires interacting with H2 at high temperatures: experimental evidence of Anomalous Heat Effects

This article is an extension of what presented by our team at 17th International Conference on Cold Fusion, ICCF-17, in Daejon, Korea, in 2012 [1]. It documents the improvements on Constantan-related experiments, started in 2011, in order to study the feasibility of new Nickel based alloys that are able to absorb proper amounts of Hydrogen (H2) and/or Deuterium (D2) and that have, in principle, some possibility to generate anomalous thermal effects at temperatures >100°C. The interest in Ni comes in part because there is the possibility to use also H2 instead of expensive D2. Moreover, cross-comparison of results using H2 instead of D2 can be made and could help the understanding of the phenomena involved (atomic, nuclear, super-chemical origin?) due to the use of such isotopes. Keywords: calorimeter, LENR, Nickel based alloys, sub-micrometric surface

Carbon nanotubes toxicology and effects on metabolism and immunological modification in vitro and in vivo

The aim of this research is focused on the biological effects of multi wall carbon nanotubes (MWCNTs) on three different human cell types, laboratory animals in vivo, and immunological effects. Large numbers of researchers are directly involved in the handling of nanostructured materials such as MWCNTs and nanoparticles. It is important to assess the potential health risks related to their daily exposure to carbon nanotubes. The administration of sterilized nanosamples has been performed on laboratory animals, in both acute and chronic administration, and the pathological effects on the parenchymal tissues have been investigated. We studied the serum immunological modifications after intraperitoneal administration of the MWCNTs. We did not observe any antigenic reaction; the screening of ANA, anti-ENA, anti-cardiolipin, C-ANCA and P-ANCA was negative. No quantitative modification of immunoglobulins was observed, hence no modification of humoral immunity was documented. We also studied the effects of MWCNTs on the proliferation of three different cell types. MCF-7 showed a significant inhibition of proliferation for all conditions studied, whereas hSMCs demonstrated a reduction of cell growth only for the highest MWCNTs concentrations after 72 h. Also, no growth modification was observed in the Caco-2 cell line. We observed that a low quantity of MWCNTs does not provoke any inflammatory reaction. However, for future medical applications, it is important to realize prosthesis based on MWCNTs, through studying the corresponding implantation effects. Moreover, it has to be emphasized that this investigation does not address, at the moment, the carcinogenicity of MWCNTs, which requires a detailed follow-up investigation on the specific topic. In view of the subsequent and more extensive use of MWCNTs, especially in applications where carbon nanotubes are injected into the human body for drug delivery, as a contrast agent carrying entities for MRI, or as the basic material of a new prosthesis generation, more extended tests and experiments are necessary. © 2008 IOP Publishing Ltd

CNT composites for aerospace applications

Carbon nanotubes were synthesized by thermal arc plasma process after optimization of the synthesis parameters. These samples were then analysed by scanning and transmission electron microscopes (SEM and TEM), in order to establish the morphology of the nanostructures. Atomic force microscopy (AFM) and electron diffraction studies were also carried out before using the sample for the composite material preparation. Composites of epoxy resin with curing agent as well as a mixture of graphite and carbon nanotubes were prepared with varying proportions of the mixture. The electrical resistivity of the material was studied under varying pressure and voltage conditions. Preliminary results of these studies present interesting features which are reported here

Characterization of the dispersion of carbon nanotubes in nanocomposites by means of a non-destructive evaluation technique

An extensive use of CNTs enhanced polymer composites can be boosted by novel NDE techniques able to check the quality of the products made of these nanocomposites in order to guarantee that their specifications are met. It is well known in literature that the parameter that much more than others can affect the enhancing capabilities of the added nanoparticles is their dispersion. All the resulting physical properties of the CNTs based polymer composites depend strongly on level of dispersion of the CNTs throughout the matrix. Here we presented a novel NDE technique based on infrared thermography able to test the dispersion of the added nanoparticles in nanocomposites. Two different procedures were selected to prepare epoxy nanocomposites with dissimilar degree of nanoparticle dispersion. The novel NDE technique was then used to compare pairs of specimens whose only difference is represented by the dispersion level, which is much better in the samples manufactured by THINKY, a vacuum planetary mixer, compared to those produced with a less efficient approach. We found a significant difference in the thermal response to the heat transfer transients, i.e. the pairs of specimens, with dissimilar level of dispersion, have clearly distinguishable thermographic outcomes. The raising up of the temperature in samples exposed to the same heat flux, is faster for those with a better level of dispersion, compared to those with a poor dispersion. Thus, the NDE technique can be used to identify consistently the thermal response of a material with respect to another. A reference product, which has the expected dispersion level and achieves the desired design performance, can be used to test the thermal behaviour of other products coming out of the production process and those with poor dispersion can be identified. The mechanisms behind the effects of MWCNTs dispersion on the thermal response of the nanocomposites to the heat transfer transients were identified: homogeneous dispersion maximizes the interface area between MWCNTs and resin, the thermal conductivity of individual MWCNTs is at least four times higher than the thermal conductivity within MWCNTs bundles, the specific heat of individual MWCNTs is one third smaller than the specific heat of MWCNTs bundles